The effects of prolonged stimulus repetition with repeated switching of target status on the orienting response in schizophrenia and depression.

Schizophrenic patients are frequently orienting nonresponders to innocuous stimuli, become responsive to significant target signals, and become hyporesponsive again on prolonged repetition. We wish to a) determine whether schizophrenic patients can display orienting response (OR) flexibility, responding to newly designated targets and ceasing to respond to newly designated nontargets; b) determine whether renewed hyporesponding can be averted with reminders of target relevance and repeated introduction of new targets; and c) compare schizophrenics with depressives and normal controls. Fifty schizophrenics (14 drug free), 50 depressives (20 drug free), and 50 normal controls receive four trial blocks involving the same sequence of 16 1000- or 2000-Hz tones delivered to either the right or left ear. A subsample of each group (N = 14) receives all blocks as a simple habituation series; others (N = 36) have to press a pedal for designated target signals (left ear or right ear, 1000 Hz or 2000 Hz), ignoring all nontarget tones. On each trial block, a new target signal is defined, and previous targets are discarded. Skin conductance and finger pulse amplitude analyses are presented. Both patient groups show enhanced ORs to newly relevant targets and ceased ORs to newly irrelevant former targets as well as normals. Both show OR decline with target repetition despite reminders and new targets.

Psychophysiological response patterns in college students with high physical anhedonia: scores appear to reflect schizotypy rather than depression.

The Chapman physical anhedonia (AN) and perceptual aberration (AB) scales were intended to identify high risk for schizophrenia. Although schizophrenic-like dysfunctions have been reported in association with each, the issue is clouded by possible relationships with depression. We recently reported psychophysiological patterns distinguishing depression from schizophrenia. Schizophrenics showed reduced orienting response (OR) to innocuous stimuli in both electrodermal (SCR) and finger pulse (FPV) components, normalizing in both to significant signals. Depressives showed deficient, non-normalizing SCR, but normal FPV, implicating SCR/cholinergic rather than OR deficits. 16 AN, 18 AB, and 17 control students received an innocuous (habituation) tone series followed by a significant (alternating-press) series. ANs displayed schizophrenic-like rather than depressive-like response patterns, but ABs showed no coherent pattern. Findings in ANs were somewhat attenuated compared with schizophrenics, perhaps reflecting the small percentage of schizophrenics-to-be in this risk group. The absence of clear deficit in ABs agrees with studies showing OR deficits to be associated with more negative symptoms in schizophrenia.

A limiting factor in the "normalization" of schizophrenic orienting response dysfunction.

Forty schizophrenic patients, 40 non-schizophrenic patients, and 40 normal subjects were given 60 each alternating 1000- and 2000-Hz, 1-second tones at 60 dB. Half of each sample, the Press Group (PG), had to press a pedal to the high (low) target tone, ignoring the nontarget tone. The other half, the Nonpress Groups (NPGs), were given no reason to attend. Skin conductance response (SCR), finger pulse volume (FPV), and electroencephalographic (EEG) activity were recorded. NPG schizophrenic subjects were more often nonresponsive in both SCR and FPV than other samples, but less often responsive in EEG only when a 20 percent criterion of alpha blockade was used. Schizophrenic subjects showed greater consistency of OR nonresponsiveness in SCR and FPV, and nonsignificantly greater consistency in criterion alpha block, pointing to a deficit in orienting response (OR) rather than in peripheral response. When the targeted signal was given, schizophrenic subjects showed the same response as other groups in all systems. This was not due to an indiscriminate increase in reactivity, since response increase centered on the targeted signal itself in all groups. As the target signal was repeated, autonomic OR in schizophrenics declined sharply so that they again became underresponsive. Thus, OR "normalization" achieved by targeting significant signals is restricted to relatively early responsiveness. The rapid decline in autonomic OR may help explain differences in schizophrenic subjects between P300 and autonomic ORs to significant stimuli. Schizophrenic subjects were no different from controls in bilateral SCR or FPV asymmetry, but displayed less frequent criterion alpha blockade and reduced background alpha power in the left hemisphere. Each system showed a different pattern of bilateral asymmetry, reflecting complex, not well understood relations among these responses. This was further emphasized by the fact that skin conductance level (SCL) incremented over trials in PG subjects, reflecting sustained activation, while EEG background showed an increase in slower wave power, consistent with reports of increased drowsiness. The only drug effect seen was a lowering of SCL. Neuroleptics were associated with a flexible inhibitory control of SCL, permitting normal-like increment when circumstances required. Depressed patients' data suggested they might show heightened OR nonresponsiveness to innocuous stimuli which might not be subject to "normalization" by manipulation of stimulus significance; hence OR deficit might still differentiate schizophrenic from depressive patients.